In a conventional circuit arrangement described in German Patent Application No. 28 20 330 C2, a motor is provided, which is controlled by a switching unit in turn influenced by a motor monitor. The motor monitor derives a reset signal from a certain static motor current value and, in addition, detects, at least occasionally, a reset signal from a certain variation of the motor current over time. In this conventional arrangement, static and dynamic monitoring is performed, whereby the motor is switched off or its direction of rotation is reversed in the event of a sudden change in torque or increase in current due, for example, to the window pane hitting an obstacle, even if the instantaneous current is relatively low. The motor, however, is switched off or its direction of rotation is reversed even if, in the event of a gradual increase in the current to a value close to short-circuit current, a rapid further increase is no longer possible. In this case, therefore, two criteria are analyzed to detect a pinching (jamming) situation: the static motor current and the variation of the motor current over time.
In general, methods of monitoring the rotation speed to limit the force and prevent pinching jamming in displacement drives such as window and sunroof motors in motor vehicles, detecting gradual or abrupt changes in the rotation speed determined, for example, using Hall sensors, and deriving the required motor control signals therefrom, are also known.